According to John Rawls’s famous Liberal Principle of Legitimacy, the exercise of political power is legitimate only if it is justifiable to all citizens. The currently dominant interpretation of what is justifiable to persons in this sense is an internalist one. On this view, what is justifiable to persons depends on their beliefs and commitments. In this paper I challenge this reading of Rawls’s principle, and instead suggest that it is most plausibly interpreted in externalist terms. On this alternative view, what is justifiable to persons is not in any way dependent on, or relativized to, their beliefs and commitments. Instead, what is justifiable to all in the relevant sense is what all could accept as free and equal. I defend this reinterpretation of the view by showing how it is supported by Rawls’s account of the freedom and equality of persons. In addition, a considerable advantage of this suggestion is that it allows for an inclusive account of to whom the exercise of political power must be made justifiable.